Abstract. A delayed chemostat model with impulsive
perturbation on the nutrient concentration and a general nutrient
uptake function is considered. The nutrient conversion process
involves time delay. Using the discrete dynamical system determined
by the stroboscopic map, we obtain the exact
microorganism-eradication periodic solution of the model and prove
the microorganism-eradication periodic solution is globally
attractive, provided that the amount of impulsive substrate is less
than some critical value. When the amount of impulsive substrate is
larger than some critical value, the system is permanent. Computer
simulations illustrate the results.